This invention relates generally to electronic arrangements which operate without making contact using proximity devices, and more particularly, to a switching arrangement having a resonant circuit which can be damped externally, an evaluation circuit, and an amplifier.
As used herein, the term "evaluation circuit" refers to a circuit for converting the output of the resonant circuit to a binary signal indicating whether an actuator is near the switch.
A known switching arrangement of the type mentioned hereinabove is described in German Pat. No. 20 54 100. In this known arrangement, a feedback oscillator is provided which can be damped by external objects. The resonant frequency of the oscillator depends upon the tolerance of the coil and the capacitor, as well as the customary components, so that the amplitude of the oscillation can change independently of objects brought in the proximity of the oscillator.
It is, therefore, an object of this invention to develop an arrangement of the aforementioned type having an oscillation amplitude which is as constant as possible in the undamped condition of the resonant circuit.
It is a further object of this invention to provide an arrangement of the type discussed hereinabove which operates substantially independently of external influences such as humidity, temperature, and the influence of adverse characteristics in its circuit components.
It is still a further object of this invention to provide an electronic switching arrangement having high sensitivity so as to operate over a large switching range.